Golf ball

ABSTRACT

A golf ball component, such as a golf ball cover layer, formed from a high or increased melt index thermoplastic polyurethane, polyurea or polyurethane/polyurea is disclosed. The cover layer may be relatively thin (i.e., 0.075 or less, preferably 0.050 inches or less, more preferably less than 0.040 inches, even more preferably less than 0.030 inches). In addition, an operation in which the outer cover is exposed to an isocyanate solution is described to improve certain physical properties of the resulting golf ball.

CROSS REFERENCES TO RELATED APPLICATIONS

The present application is a continuation application of U.S. patentapplication Ser. No. 11/748,025, filed on May 14, 2007, which is acontinuation application of U.S. patent application Ser. No. 11/539,565,filed on Oct. 6, 2006, now U.S. Pat. No. 7,217,200, which is acontinuation application of U.S. patent application Ser. No. 11/056,719,filed on Feb. 11, 2005, now U.S. Pat. No. 7,118,496, which is adivisional application of U.S. patent application Ser. No. 10/626,937,filed on Jul. 25, 2003, now U.S. Pat. No. 6,855,076, which claimspriority from U.S. Provisional Patent Application No. 60/398,379, filedJul. 25, 2002 and now is abandoned.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to golf balls, preferably golf balls witha polyurethane, polyurea or polyurethane/polyurea component, such as acover layer, having improved durability for repetitive play.

2. Description of the Related Art

Traditional golf ball covers have been comprised of balata or blends ofbalata with elastomeric or plastic materials. The traditional balatacovers are relatively soft and flexible. Upon impact, the soft balatacovers compress against the surface of the club producing high spin.Consequently, the soft and flexible balata covers provide an experiencedgolfer with the ability to apply a spin to control the ball in flight inorder to produce a draw or a fade, or a backspin which causes the ballto “bite” or stop abruptly on contact with the green. Moreover, the softbalata covers produce a soft “feel” to the low handicap player. Suchplayability properties (workability, feel, etc.) are particularlyimportant in short iron play with low swing speeds and are exploitedsignificantly by relatively skilled players.

Despite all the benefits of balata, balata covered golf balls are easilycut and/or damaged if mis-hit. Golf balls produced with balata orbalata-containing cover compositions therefore have a relatively shortlife span.

As a result of this negative property, balata and its syntheticsubstitutes, transpolybutadiene and transpolyisoprene, have beenessentially replaced as the cover materials of choice by other covermaterials such as ionomeric resins and polyurethanes.

Ionomeric resins are polymers containing interchain ionic bonding. As aresult of their toughness, durability and flight characteristics,various ionomeric resins sold by E.I. DuPont de Nemours & Company underthe trademark Surlyn® and by the Exxon Corporation (see U.S. Pat. No.4,911,451) under the trademarks Escor® and Iotek®, have become widelyutilized for the construction of golf ball covers over the traditional“balata” (transpolyisoprene, natural or synthetic) rubbers. As stated,the softer balata covers, although exhibiting enhanced playabilityproperties, lack the durability (cut and abrasion resistance, fatigueendurance, etc.) properties required for repetitive play.

Ionomeric resins are generally ionic copolymers of an olefin, such asethylene, and a metal salt of an unsaturated carboxylic acid, such asacrylic acid, methacrylic acid, or maleic acid. Metal ions, such assodium or zinc, are used to neutralize some portion of the acidic groupsin the copolymer resulting in a thermoplastic elastomer exhibitingenhanced properties, such as durability, for golf ball coverconstruction over balata. However, some of the advantages gained inincreased durability have been offset to some degree by the decreasesproduced in playability. This is because although the ionomeric resinsare very durable, they tend to be very hard when utilized for golf ballcover construction, and thus lack the degree of softness required toimpart the spin necessary to control the ball in flight. Since theionomeric resins are harder than balata, the ionomeric resin covers donot compress as much against the face of the club upon impact, therebyproducing less spin. In addition, the harder and more durable ionomericresins lack the “feel” characteristic associated with the softer balatarelated covers.

As a result, while there are many different commercial grades ofionomers available both from DuPont and Exxon, with a wide range ofproperties which vary according to the type and amount of metal cations,molecular weight, composition of the base resin (for example, relativecontent of ethylene and methacrylic and/or acrylic acid groups) andadditive ingredients such as reinforcement agents, etc., a great deal ofresearch continues in order to develop a golf ball cover compositionexhibiting not only the improved impact resistance and carrying distanceproperties produced by the “hard” ionomeric resins, but also theplayability (for example, “spin”, “feel”, etc.) characteristicspreviously associated with the “soft” balata covers, properties whichare still desired by the more skilled golfer.

Furthermore, a number of different golf ball constructions, such asone-piece, two-piece (a solid resilient center or core with a moldedcover), three-piece (a liquid or solid center, elastomeric winding aboutthe center, and a molded cover), and multi-piece golf balls, have beendeveloped to produce golf balls exhibiting enhanced playability anddurability. The different types of materials utilized to formulate thecores, mantles, windings, covers, etc. of these balls dramaticallyalters the balls' overall characteristics. In addition, multi-layeredcovers containing one or more ionomer resins or other materials havealso been formulated in an attempt to produce a golf ball having theoverall distance, playability and durability characteristics desired.

For example, in various attempts to produce a durable, high spin golfball, the golfing industry has blended the hard ionomer resins with anumber of softer ionomeric resins and applied these blends to two-pieceand three-piece golf balls. U.S. Pat. Nos. 4,884,814 and 5,120,791 aredirected to cover compositions containing blends of hard and softionomeric resins. However, it has been found that golf ball coversformed from hard-soft ionomer blends tend to become scuffed more readilythan covers made of hard ionomer alone. Consequently, it would be usefulto develop a golf ball having a combination of softness and durabilitywhich is better than the softness-durability combination of a golf ballcover made from a hard-soft ionomer blend.

Additionally, thermoset and thermoplastic polyurethanes have recentlybecome popular materials of choice for golf ball cover construction.However, these polyurethanes are difficult and time consuming toprocess. Moreover, the molding of relatively thin wall cover layer(s),i.e., cover layers 0.075 inches or less in cross-sectional thickness, isdifficult to accomplish. This limits the desired performance achieved bythin wall cover molding, such as improved distance. Furthermore, golfballs produced utilizing these materials tend to be soft and readilysusceptible to scuffing.

As a result, it would be further desirable to produce a thermoplasticpolyurethane covered golf ball having a thin wall cover constructionwhich exhibits enhanced durability, namely improved cut and scuff(groove shear) resistance, while maintaining and/or improving suchcharacteristics as playability and distance.

BRIEF SUMMARY OF THE INVENTION

An object of the invention is to provide a golf ball with a soft,polyurethane, polyurea or polyurethane/polyurea golf ball componenthaving improved durability for repetitive play. Another object of theinvention is to provide a method of making such a golf ball.

A further object of the invention is to provide a golf ball with a soft,low flex modulus thermoplastic polyurethane, polyurea orpolyurethane/polyurea outer cover component having enhanced durabilitywhile maintaining or improving the playability properties of the ball,as well as a method of making the same.

An additional object of the invention is to provide a golf or game ballwith a thin, thermoplastic polyurethane, polyurea orpolyurethane/polyurea outer cover layer having improved playability,distance and cut resistance. Also included is a process for producingsuch a ball.

A still further object is to produce a high melt index thermoplasticpolyurethane, polyurea or polyurethane/polyurea (TPU) golf ballcomponent, such as the outer cover layer of a golf ball. Preferably, thecover is of thin wall (i.e., 0.075 inches or less, preferably 0.040inches or less, more preferably 0.030 inches or less and most preferably0.025 inches or less) construction. A process for producing such a highmelt index cover is also included in the present invention.

A still additional object is to produce a molded golf ball componentproduced from a high melt index, thermoplastic polyurethane, polyurea orpolyurethane/polyurea material. The material has a melt index of 15 g/10min, preferably 20 g/10 min or more, more preferably 25 g/10 min or moreat a temperature of 200° C. to 210° C. and a load of 8.7 Kg prior tomolding. Subsequent to molding, the molded golf ball component istreated with a secondary surface curing agent, such as an isocyanatesolution, to produce a soft, yet durable golf ball component.

Another object of the invention is to produce a golf ball having a corewith a relatively thin cover layer molded thereon. The cover layer isproduced from a polyurethane, polyurea or polyurethane/polyurea materialhaving a high melt index. The melt index of the material is 15 g/10 minor more, preferably 20 g/10 min or more, and more preferably 25 g/10 minor more, even more preferably 30 g/10 min or more and most preferably 35g/10 min or more, at a temperature of 200° C. to 210° C. and a load of8.7 Kg prior to molding. Subsequent to molding, the cover layer of thegolf ball is treated with an isocyanate solution. The resulting productexhibits enhanced playability and durability characteristics.

Yet another object is to produce a multi-piece golf ball having a thin,yet soft, outer cover layer. The outer cover layer is molded from athermoplastic polyurethane, polyurea or polyurethane/polyurea materialhaving a high melt index. The melt index of the material is 15 g/10 minor more, preferably 20 g/10 min or more, and more preferably 25 g/10 minor more, even more preferably 30 g/10 min or more, and most preferably35 g/10 min or more, at a temperature of 200° C. to 210° C. and a loadof 8.7 Kg prior to molding. After the molding step, the cover of thegolf ball is subjected to treatment for an effective period of time,with a secondary curing agent, such as an isocyanate solution containingone or more isocyanates to improve the cover's durability. Themulti-piece golf ball produced exhibits enhanced characteristics inplayability and durability.

Still another object of the invention is to produce a molded golf ballcomponent, such as a molded golf ball cover layer, comprising athermoplastic material wherein the melt index of the material isincreased at least 10%, most preferably 100% or more, prior to molding.The thermoplastic material comprises polyurethane, polyurea or blendsthereof. The process of producing such a component is also includedherein.

Other objects will be in part obvious and in part pointed out more indetail hereafter.

In this regard, the invention is directed, in part, to a golf ballcomponent produced from a thermoplastic polyurethane, polyurea orpolyurethane/polyurea (TPU) material having a high melt index.Alternatively, the golf ball component is produced from a polyurethane,polyurea or polyurethane/polyurea material wherein the melt index of thematerial is increased approximately 10% or more, preferably 20% or more,more preferably 50% or more, and most preferably 100% or more, prior tomolding. Preferably, the component is the outer cover layer of a golfball, such as a two-piece, three-piece or multi-piece golf ball.

In another aspect, the present invention is directed to the process ofproducing a thermoplastic polyurethane, polyurea orpolyurethane/polyurea golf ball component, the processes comprising thesteps of obtaining or producing a thermoplastic polyurethane, polyureaor polyurethane/polyurea material having a high melt index prior tomolding. The high melt index material can be produced by converting alow melt index thermoplastic material into a higher melt index material.This is optimally produced by further processing or refining thematerial. Preferably, the material is refined by lowering the molecularweight of the material such as by mechanical (i.e., extrusion, etc.) andchemical means. However, other mechanisms for increasing the melt indexof the material can be utilized. The higher melt index material producedthereby is then molded into a golf ball component such as a cover. Thecomponent so produced may also be subsequently treated with a secondarycuring agent, such as an isocyanate solution, to enhance the component'sdurability. The present invention is also directed to the golf ballcomponent produced using such a process.

In a further aspect, the present invention is directed to a process forproducing a golf ball having a relatively thin (i.e., 0.075 inches orless, preferably 0.050 inches or less, more preferably 0.040 inches orless) cover comprising a high melt index, thermoplastic polyurethane,polyurea or polyurethane/polyurea (TPU) material. The process comprisesthe steps of obtaining a base thermoplastic polyurethane, polyurea orpolyurethane/polyurea material, increasing the melt index of the basematerial at least 10% (preferably 20% or more, more preferably 50% ormore, and most preferably 100% or more), and molding the increased meltindex thermoplastic polyurethane material into a very thin golf ballcover. The very thin golf ball cover is then subsequently treated with asecondary curing agent, such as an isocyanate solution. This produces arelatively soft, very thin cover layer having improved durability. Inanother aspect, the present invention relates to the golf ball coverproduced by this process.

In still another aspect, the present invention relates to a process forproducing a high melt index, thermoplastic polyurethane, polyurea orpolyurethane/polyurea (TPU) golf component having improved durability.The process comprises the steps of obtaining a base thermoplasticpolyurethane, polyurea or polyurethane/polyurea material, increasing themelt index of the base material at least 10% (most preferably about 100%or more), molding the increased melt index thermoplastic material into agolf ball component, and treating the molded golf ball component with anisocyanate solution.

In an additional aspect, the present invention provides a golf ballcomprising a core with a cover disposed on the core. The cover includesa polyurethane material having a high melt index of from about 15 g/10min or more, preferably 20 k/10 min or more, and more preferably 25 toabout 150 grams per 10 minutes at a temperature of 200° C. to 210° C.and a load of 8.7 kg prior to molding. The cover is subsequently treatedwith an isocyanate or a mixture of isocyanates for an effective periodof time to enhance its durability.

In another aspect, the present invention provides a golf ball comprisinga core with an outer cover disposed on the core. The cover is formedfrom a polymeric cover composition that includes a polyurethane. Thecover composition has a melt index prior to forming the cover of fromabout 35 to about 85 grams per 10 minutes at a temperature of 200° C. to210° C. and a load of 8.7 kg. Subsequent to molding, the cover istreated with a secondary curing agent such as an isocyanate solution.The golf ball may also include one or more intermediate layers betweenthe core and the outer cover layer.

In a further aspect, the present invention provides a method forproducing a golf ball. The method comprises the steps of providing acore material and forming a core from that core material. A covermaterial is provided in which the cover material includes apolyurethane, polyurea or polyurethane/polyurea, having a melt index offrom about 15 g/10 min or more, preferably 20 g/10 min or more, and morepreferably 25 to about 150 grams per 10 minutes at a temperature of 200°C. to 210° C. and a load of 8.7 kg. The method additionally includes thesteps of forming a cover layer from the cover material about the coreand treating the cover layer with a solution of isocyanates.

In yet another aspect, the present invention provides a method forproducing a multi-piece golf ball with a soft, yet durable cover forrepetitive play. The method comprises a step of providing a corematerial and forming a molded core from the core material. The methodadditionally comprises the step of providing a cover material in whichthe cover material includes a polyurethane, polyurea or blends thereofhaving a flex modulus of 30,000 psi or less (plaque), preferably 20,000or less, and more preferably 15,000 or less, and a Shore D of 60 or less(plaque), preferably 55 or less, more preferably 50 or less and mostpreferably 45 or less. The cover material exhibits a melt index of fromabout 15 g/10 min or more, preferably 20 g/10 min or more, and morepreferably 25 to about 150 grams per 10 minutes at a temperature of 200°C. to 210° C. and a load of 8.7 kg prior to molding. The method furthercomprises the steps of molding a cover layer from the cover materialabout the core and then treating the molded cover layer with anisocyanate solution. This aspect also includes the soft covered,multi-piece golf ball produced by such a process.

In still another aspect, the present invention provides a method ofproducing a multi-piece golf ball. The method comprises a step ofproviding a core material, forming a core from that core material,providing a cover material in which the cover material includes a lowflex modulus (i.e., having a flex modulus of 30,000 or less (plaque),preferably 20,000 or less, and more preferably 15,000 or less),polyurethane, polyurea or polyurethane/polyurea material in which themelt index of the material has been increased prior to molding at least10% or more, preferably 20% or more, more preferably 50% or more, andmost preferably 100% or more, from supplied base or virgin material torefined or processed material, and molding a cover layer from thatmaterial. The method additionally includes a step of applying a solutionof one or more isocyanates to the molded cover layer for a time periodof from about 1 minute to about 10 minutes.

The invention accordingly comprises the several steps and the relationof one or more of such steps with respect to each of the others and thearticles possessing the features, properties, and the relation ofelements exemplified in the following detailed disclosure.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

The following is a brief description of the drawings, which arepresented for the purposes of illustrating the invention and not for thepurposes of limiting the same.

FIG. 1 is a cross-sectional view of a golf ball 8 embodying theinvention illustrating a core 10 and a cover 12 consisting of an innerlayer 14 and an outer layer 16;

FIG. 2 is a diametrical cross-sectional view of a golf ball 8 of theinvention having a core 10 and a cover 12 made of an inner layer 14 andan outer layer 16; and

FIG. 3 is a cross-sectional view of a golf ball 8 embodying theinvention illustrating a dual core having an inner core 20 and a corelayer 22, and a cover 12 consisting of an inner layer 14 and an outerlayer 16.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is directed to a molded golf ball component, suchas a golf ball cover layer that is comprised of a soft, high melt indexthermoplastic polyurethane, polyurea or polyurethane/polyurea material.Preferably, the golf ball component comprises a relatively thin (i.e.,0.075 inches or less, preferably 0.050 inches or less, more preferably0.040 inches or less, even more preferably 0.030 inches or less, andmost preferably 0.025 inches or less) outer cover layer. The golf ballcomponent can then be optionally exposed to a secondary curing,cross-linking or treating agent, such as a solution of isocyanate, toimprove certain characteristics (such as durability, etc.) of theresulting molded component.

Along these lines, the present invention concerns the production of athermoplastic polyurethane, polyurea or polyurethane/polyurea golf ballcomponent wherein the melt index of polyurethane, polyurea orpolyurethane/polyurea material is high (i.e., 15 g/10 min or more,preferably 20 g/10 min or more, more preferably greater than 25 gramsper 10 minutes at the temperature of 200° C. to 210° C. and a load of8.7 Kg) or substantially increased prior to molding. For example, themelt index of the material can be increased, from supplied or basematerial to refined or processed material, at least 10% or more,preferably 20% to 720%, more preferably 50% to 720%, and most preferably100% or more prior to molding.

The enhanced melt index of the material may be achieved by secondaryprocessing or refining steps, such as by mechanical, chemical orelectrical means. Preferably, the melt index is increased by mechanicalmeans such as by extrusion. While not wanting to be limited to thetheory of such an increase, it is believed that the melt index increasesafter extrusion due to a decrease in molecular weight, either bymechanical shearing or chemical changes or both. Additional processesfor decreasing the molecular weight of the material can also be used.For example, other methods for decreasing the molecular weight and/orincreasing the melt index of the material include the use of, or theincorporation of, heat, light, irradiation, moisture, flow additives,plasticizers, extenders, lubricants or other thermoplastic materialshaving a higher melt index, etc. The melt index of the material isadjusted to the high melt index range desired prior to molding.

In a further embodiment, the golf ball component, such as a golf ballcover, is treated with a secondary curing or treating agent, such as asolution containing one or more isocyanates, to improve durability ofthe component. It is believed that the isocyanate further cross-linksthe cover material to provide additional scuff resistance whilemaintaining the other desirable features of the cover, such as softnessand feel. The solution containing the isocyanate is added to the outercover layer by any suitable method known in the art, although dipping,wiping, soaking, brushing or spraying the golf ball in or with theisocyanate solution is preferred. The method of adding the isocyanate tothe cover layer is discussed in more detail below.

The solution of the isocyanate that is added to the cover layer toimprove scuff resistance can be any aliphatic or aromatic isocyanate ordiisocyanate or blends thereof known in the art. The isocyanate ordiisocyanate used may have a solids content in the range of about 1 toabout 100 weight %, preferably about 5 to about 50 weight %, mostpreferably about 10 to about 30 weight %. If it is necessary to adjustthe solids content, any suitable solvent that will allow penetration ofthe isocyanate into the polyurethane, polyurea or polyurethane/polyureacover material without causing distortion may be used. Examples ofsuitable solvents include ketone and acetate.

In a particularly preferred aspect of the present invention, the coverlayer is relatively thin (i.e., 0.075 inches or less) and is formed froma thermoplastic polyurethane, polyurea or polyurethane/polyurea materialhaving a relatively high melt index, or that which is adjusted prior tomolding so as to exhibit a relatively high melt index. In this regard,the melt of the material is 25 g/10 min or more at a temperature of 200°C. to 210° C. and a load of 8.7 kg prior to molding. Preferably, themelt index of the material is of 30 g/10 min or more, more preferably 35g/10 min or more and most preferably 40 g/10 min or more at the abovenoted temperature and conditions.

In accordance with the present invention, it has been discovered thatthe higher the melt index of a polymer, the better the flow and lowerthe injection molding pressures, and thus, the greater the ability tomold thin cross sections. If the melt index values were not adjustedhigher in this fashion, thin wall cover molding would not be possiblewith certain materials, thereby limiting the performance achieved bythin wall cover molding (mainly improved distance). Melt index or meltflow values referred to herein are determined (unless specifieddifferently) in accordance with ASTM Standard D1238, herein incorporatedby reference.

The previously noted preferred thermoplastic polyurethane materials maybe adjusted into higher melt index materials prior to their use as golfball cover materials. It is necessary to raise melt index to allow forthe molding of a relatively thin wall cover over golf ball cores (i.e.,covers less than 0.075). For example, Bayer Texin® DP7-1097 has(according to Bayer Corporation) a melt index of about 7 to 12 g/10 minat 200° C. and 8.7 kg. The base material received from Bayer is thenfurther processed to exhibit a melt index of from about 25 to about 45g/10 min at 200° C. and 8.7 kg. This material, when used for forming agolf ball cover layer as described herein and including whitemasterbatch material, preferably has an increased melt index of about 35to about 85 g/10 min at 200° C. and 8.7 kg.

Similarly, Bayer Texin® 245 has (according to Bayer Corporation) a meltindex of about 20 to 40 g/10 min at 230° C. and 1.2 kg. It can befurther processed or refined to exhibit a melt index of about 25 toabout 45 g/10 min at 210° C. and 8.7 kg. Additionally, the melt index ofthe material can be farther adjusted by adding white masterbatch so themelt index is about 35 to about 85 g/10 min at 210° C. and 8.7 kg priorto molding.

As also noted herein, it has been discovered that as the melt index of apolymer increases, some of the physical properties of the polymerdecrease. As a result, in the more preferred embodiments of theinvention the high melt index golf ball components are further treatedwith a liquid isocyanate solution. By performing an isocyanatepost-molding treatment process to the golf ball, the physical propertiesof the thermoplastic polyurethane, polyurea or polyurethane/polyureacover material may not only increase, but may increase beyond the valuesof the non-refined material. This physical property improvement yields asignificant improvement in golf ball durability, namely improved cut andscuff (groove shear) resistance.

This post-application of isocyanate is believed to allow for the use ofrelatively high melt index thermoplastic polyurethane, polyurea orpolyurethanes/polyureas to be used in conventional injection moldingmachines and/or in reaction injection molding (“RIM”) equipment to moldthin wall layers, i.e. 0.075 inches, more preferably 0.050 inches andbelow, preferably 0.040 inches and below, more preferably 0.030 inchesand below, and most preferably 0.025 inches and below. The moldedthin-walled golf balls are preferably dipped in an isocyanate solutionfor 1 to 10 minutes (preferably 1 to 5 minutes); the isocyanate may bealiphatic or aromatic, such as HDI, IPDI, MDI, TDI type or others asdiscussed below and the isocyanate solution may range from 10 to 100%solids. The solvent used to reduce the solids and make the isocyanatesolutions may be a ketone or acetate or any solvent that will allowpenetration of the isocyanate into the cover material without distortingthe cover. After dipping, the balls are air-dried for 1 hour and thenpost-cured at 175° F. for 4 hours. After the post-cure the balls may becleaned with isopropanol to remove any excess isocyanate from the coverand the balls are then finished in a normal manner. Preferably, theisocyanate used is of the MDI type at 15-30% solids reduced with aketone (such as Mondur ML™ from Bayer Corporation) and dipped for 2-3minutes. Most preferably, the solids level is about 16 to 24% (20±4). Itis beneficial that the MDI remain in a liquid state at room temperature.However, this method shall not be limited to the type of polyurethane,polyurea or polyurethane/polyurea material, isocyanate used,concentration of the isocyanate solution, solvent used, dip time, ormethod of application described above.

The cover is preferably a multi-layer cover comprising a harder innercover layer formed over the core, the inner cover layer having a Shore Dhardness of at least 60 (or at least about 80 Shore C) as measured onthe surface thereof, and a softer outer cover layer comprisingthermoplastic polyurethane, polyurea or polyurethane/polyurea formedover the inner cover layer, the outer cover layer having a Shore Dhardness of less than 60, preferably a Shore D hardness of 55 or less,more preferably 50 or less, and most preferably 45 or less, as measuredon the surface thereof, the golf ball cover having improved scuffresistance. The cover may optionally comprise additional layers. In sucha golf ball, the present invention is directed, in part, to the processof producing the soft, outer cover layers.

In another aspect, the present invention provides a golf ball comprisinga core, a hard inner cover layer formed over the core, and a softerouter cover layer formed over the inner cover layer. The inner coverlayer has a Shore D hardness of at least 60 (or at least about 80 ShoreC) as measured on the curved surface thereof and is formed of acomposition including at least one material selected from the group ofconsisting of ionomers, polyamides, polyurethanes, polyureas, polyesterelastomers, polyester amides, metallocene catalyzed polyolefins, andblends thereof. The outer cover layer has a Shore D hardness of lessthan 60, preferably a Shore D hardness of 55 or less, more preferably 50or less, and most preferably 45 or less as measured on the curvedsurface thereof. It is formed from a composition comprising at least onethermoplastic polyurethane, polyurea or polyurethane/polyurea materialhaving an increased melt index. The golf ball cover has improved scuffresistance.

Referring to the FIGS. 1-3, the present invention relates to improvedmulti-layer golf balls, particularly a golf ball 8 comprising amulti-layered cover 12 over a solid core 10, and method for making same.The golf balls of the invention can be of a standard or enlarged size,and the outer cover layer has improved scuff resistance. The core mayhave multiple layers, such as a dual core as shown in FIG. 3 having aspherical center or inner core 20 and a core layer 22 surrounding theinner core. Additional core layers may also be present. The cover layeris preferably a multi-layer cover comprising at least an inner coverlayer and an outer cover, although any number of cover layers, such as2, 3, 4, 5 or more is possible.

The core 10, or the dual core 20, 22, of the golf ball can be formed ofa solid, a liquid, or any other substance that will result in an innerball (core and inner cover layer), having the desired COR, compressionand hardness. The multi-layered cover 12 comprises two layers: a firstor inner layer or ply 14 and a second or outer layer or ply 16. Theinner layer 14 can be ionomer, ionomer blends, non-ionomer, non-ionomerblends, or blends of ionomer and non-ionomer. The outer layer 16 ispreferably softer than the inner layer and can be polyurethane,polyurea, polyurethane/polyurea blends, or a blend of apolyurethane/polyurea and ionomer or non-ionomer.

In a further embodiment, the inner layer 14 is comprised of a hard, highacid (i.e. greater than 16 weight percent acid) ionomer resin or highacid ionomer blend. Preferably, the inner layer is comprised of a blendof two or more high acid (i.e. at least 16 weight percent acid) ionomerresins neutralized to various extents by different metal cations. Theinner cover layer may or may not include a metal stearate (e.g., zincstearate) or other metal fatty acid salt. The purpose of the metalstearate or other metal fatty acid salt is to lower the cost ofproduction without affecting the overall performance of the finishedgolf ball. In an additional embodiment, the inner layer 14 is comprisedof a hard, low acid (i.e. 16 weight percent acid or less) ionomer blend.Preferably, the inner layer is comprised of a blend of two or more lowacid (i.e. 16 weight percent acid or less) ionomer resins neutralized tovarious extents by different metal cations. The inner cover layer may ormay not include a metal stearate (e.g., zinc stearate) or other metalfatty acid salt.

It has been found that a hard inner layer provides for a substantialincrease in resilience (i.e., enhanced distance) over known multi-layercovered balls. The softer outer layer provides for desirable “feel” andhigh spin rate while maintaining respectable resiliency. The soft outerlayer allows the cover to deform more during impact and increases thearea of contact between the clubface and the cover, thereby impartingmore spin on the ball. As a result, the soft cover provides the ballwith a balata-like feel and playability characteristics with improveddistance and durability. Consequently, the overall combination of theinner and outer cover layers results in a golf ball having enhancedresilience (improved travel distance) and durability (i.e. cutresistance, etc.) characteristics while maintaining and in manyinstances, improving, the playability properties of the ball.

The combination of a hard inner cover layer or layers with a soft,relatively low modulus polyurethane, polyurea or polyurethane/polyureaouter cover layer provides for excellent overall coefficient ofrestitution (for example, excellent resilience) because of the improvedresiliency produced by the inner cover layer. While some improvement inresiliency is also produced by the outer cover layer, the outer coverlayer generally provides for a more desirable feel and high spin,particularly at lower swing speeds with highly lofted clubs such as halfwedge shots.

The particular parameters of the various components of the golf balls,as well as the methods for making the same are more specifically setforth below.

Inner Cover Layer(s)

Preferably, the inner cover layer is harder than the outer cover layerand generally has a thickness in the range of 0.010 to 0.150 inches,preferably 0.010-0.100 inches, more preferably 0.020 to 0.060 inches fora 1.68 inch ball and 0.030 to 0.100 inches for a 1.72 inch (or more)ball. The core and inner cover layer together form an inner ball havinga coefficient of restitution of 0.780 or more and more preferably 0.790or more, and a diameter in the range of 1.48 to 1.67 inches for a 1.68inch ball and 1.50 to 1.71 inches for a 1.72 inch (or more) ball. Theinner cover layer has a Shore D hardness of 60 or more (or at leastabout 80 Shore C). It is particularly advantageous if the golf balls ofthe invention have an inner layer with a Shore D hardness of 65 or more(or at least about 100 Shore C). If the inner layer is too thin, it isvery difficult to accurately measure the Shore D, and sometimes theShore C, of the inner layer as the layer may puncture. Additionally, ifthe core is harder, this will sometimes influence the reading. If theShore C or Shore D is measured on a plaque of material, different valueswill result. The above-described characteristics of the inner coverlayer provide an inner ball having a PGA compression of 100 or less. Itis found that when the inner ball has a PGA compression of 90 or less,excellent playability results.

The inner layer compositions of the embodiments described herein mayinclude the high acid ionomers such as those developed by E.I. DuPont deNemours & Company under the trademark Surlyn® and by Exxon Corporationunder the trademarks Escor® or Iotek®, or blends thereof.

The high acid ionomers which may be suitable for use in formulating theinner layer compositions of various embodiments of the invention areionic copolymers which are the metal, (such as sodium, zinc, magnesium,etc.), salts of the reaction product of an olefin having from about 2 to8 carbon atoms and an unsaturated monocarboxylic acid having from about3 to 8 carbon atoms. Preferably, the ionomeric resins are copolymers ofethylene and either acrylic or methacrylic acid. In some circumstances,an additional comonomer such as an acrylate ester (for example, iso- orn-butylacrylate, etc.) can also be included to produce a softerterpolymer. The carboxylic acid groups of the copolymer are partiallyneutralized (for example, approximately 10-100%, preferably 30-70%) bythe metal ions. Each of the high acid ionomer resins which may beincluded in the inner layer cover compositions of the invention containsgreater than about 16% by weight of a carboxylic acid, preferably fromabout 17% to about 25% by weight of a carboxylic acid, more preferablyfrom about 18.5% to about 21.5% by weight of a carboxylic acid.

The high acid ionomeric resins available from Exxon under thedesignation Escor® or Iotek®, are somewhat similar to the high acidionomeric resins available under the Surlyn® trademark. However, sincethe Escor®/Iotek® ionomeric resins are sodium or zinc salts ofpoly(ethylene-acrylic acid) and the Surlyn® resins are zinc, sodium,magnesium, etc. salts of poly(ethylene-methacrylic acid), distinctdifferences in properties exist.

Examples of the high acid methacrylic acid based ionomers found suitablefor use in accordance with this invention include Surlyn® 8220 and 8240(both formerly known as forms of Surlyn® AD-8422), Surlyn® 9220 (zinccation), Surlyn® SEP-503-1 (zinc cation), and Surlyn® SEP-503-2(magnesium cation). According to DuPont, all of these ionomers containfrom about 18.5 to about 21.5% by weight methacrylic acid.

Examples of the high acid acrylic acid based ionomers suitable for usein the present invention also include the Escor® or Iotek® high acidethylene acrylic acid ionomers produced by Exxon such as Ex 1001, 1002,959, 960, 989, 990, 1003, 1004, 993, 994. In this regard, Escor® orIotek® 959 is a sodium ion neutralized ethylene-acrylic neutralizedethylene-acrylic acid copolymer. According to Exxon, Ioteks® 959 and 960contain from about 19.0 to about 21.0% by weight acrylic acid withapproximately 30 to about 70 percent of the acid groups neutralized withsodium and zinc ions, respectively.

Furthermore, as a result of the development by the assignee of thisapplication of a number of high acid ionomers neutralized to variousextents by several different types of metal cations, such as bymanganese, lithium, potassium, calcium and nickel cations, several highacid ionomers and/or high acid ionomer blends besides sodium, zinc andmagnesium high acid ionomers or ionomer blends are now available forgolf ball cover production. It has been found that these additionalcation neutralized high acid ionomer blends produce inner cover layercompositions exhibiting enhanced hardness and resilience due tosynergies that occur during processing. Consequently, the metal cationneutralized high acid ionomer resins recently produced can be blended toproduce substantially higher C.O.R.'s than those produced by the lowacid ionomer inner cover compositions presently commercially available.

More particularly, several metal cation neutralized high acid ionomerresins have been produced by the assignee of this invention byneutralizing, to various extents, high acid copolymers of analpha-olefin and an alpha, beta-unsaturated carboxylic acid with a widevariety of different metal cation salts. This discovery is the subjectmatter of U.S. application Ser. No. 08/493,089, now U.S. Pat. No.5,688,869, incorporated herein by reference. It has been found thatnumerous metal cation neutralized high acid ionomer resins can beobtained by reacting a high acid copolymer (i.e. a copolymer containinggreater than 16% by weight acid, preferably from about 17 to about 25weight percent acid, and more preferably about 20 weight percent acid),with a metal cation salt capable of ionizing or neutralizing thecopolymer to the extent desired (for example, from about 10% to 90%).

The base copolymer is made up of greater than 16% by weight of an alpha,beta-unsaturated carboxylic acid and an alpha-olefin. Optionally, asoftening comonomer can be included in the copolymer. Generally, thealpha-olefin has from 2 to 10 carbon atoms and is preferably ethylene,and the unsaturated carboxylic acid is a carboxylic acid having fromabout 3 to 8 carbons. Examples of such acids include acrylic acid,methacrylic acid, ethacrylic acid, chloroacrylic acid, crotonic acid,maleic acid, fumaric acid, and itaconic acid, with acrylic acid beingpreferred.

The softening comonomer that can be optionally included in the innercover layer for the golf ball of the invention may be selected from thegroup consisting of vinyl esters of aliphatic carboxylic acids whereinthe acids have 2 to 10 carbon atoms, vinyl ethers wherein the alkylgroups contains 1 to 10 carbon atoms, and alkyl acrylates ormethacrylates wherein the alkyl group contains 1 to 10 carbon atoms.Suitable softening comonomers include vinyl acetate, methyl acrylate,methyl methacrylate, ethyl acrylate, ethyl methacrylate, butyl acrylate,butyl methacrylate, or the like.

Consequently, examples of a number of copolymers suitable for use toproduce the high acid ionomers included in the present inventioninclude, but are not limited to, high acid embodiments of anethylene/acrylic acid copolymer, an ethylene/methacrylic acid copolymer,an ethylene/itaconic acid copolymer, an ethylene/maleic acid copolymer,an ethylene/methacrylic acid/vinyl acetate copolymer, anethylene/acrylic acid/vinyl alcohol copolymer, etc. The base copolymerbroadly contains greater than 16% by weight unsaturated carboxylic acid,from about 39 to about 83% by weight ethylene and from 0 to about 40% byweight of a softening comonomer. Preferably, the copolymer containsabout 20% by weight unsaturated carboxylic acid and about 80% by weightethylene. Most preferably, the copolymer contains about 20% acrylic acidwith the remainder being ethylene.

Along these lines, examples of the preferred high acid base copolymerswhich fulfill the criteria set forth above, are a series ofethylene-acrylic copolymers which are commercially available from TheDow Chemical Company, Midland, Mich., under the Primacor® designation.

The metal cation salts utilized in the invention are those salts whichprovide the metal cations capable of neutralizing, to various extents,the carboxylic acid groups of the high acid copolymer. These includeacetate, oxide or hydroxide salts of lithium, calcium, zinc, sodium,potassium, nickel, magnesium, and manganese.

Examples of such lithium ion sources are lithium hydroxide monohydrate,lithium hydroxide, lithium oxide and lithium acetate. Sources for thecalcium ion include calcium hydroxide, calcium acetate and calciumoxide. Suitable zinc ion sources are zinc acetate dihydrate and zincacetate, a blend of zinc oxide and acetic acid. Examples of sodium ionsources are sodium hydroxide and sodium acetate. Sources for thepotassium ion include potassium hydroxide and potassium acetate.Suitable nickel ion sources are nickel acetate, nickel oxide and nickelhydroxide. Sources of magnesium include magnesium oxide, magnesiumhydroxide, and magnesium acetate. Sources of manganese include manganeseacetate and manganese oxide.

The metal cation neutralized high acid ionomer resins are produced byreacting the high acid base copolymer with various amounts of the metalcation salts above the crystalline melting point of the copolymer, suchas at a temperature from about 200□F to about 500□F, preferably fromabout 250□F to about 350□F under high shear conditions at a pressure offrom about 10 psi to 10,000 psi. Other well known blending techniquesmay also be used. The amount of metal cation salt utilized to producethe new metal cation neutralized high acid based ionomer resins is thequantity which provides a sufficient amount of the metal cations toneutralize the desired percentage of the carboxylic acid groups in thehigh acid copolymer. The extent of neutralization is generally fromabout 10% to about 90%.

A number of different types of metal cation neutralized high acidionomers can be obtained from the above-indicated process. These includehigh acid ionomer resins neutralized to various extents with manganese,lithium, potassium, calcium and nickel cations. In addition, when a highacid ethylene/acrylic acid copolymer is utilized as the base copolymercomponent of the invention and this component is subsequentlyneutralized to various extents with the metal cation salts producingacrylic acid based high acid ionomer resins neutralized with cationssuch as sodium, potassium, lithium, zinc, magnesium, manganese, calciumand nickel, several cation neutralized acrylic acid based high acidionomer resins are produced.

When compared to low acid versions of similar cation neutralized ionomerresins, the new metal cation neutralized high acid ionomer resinsexhibit enhanced hardness, modulus and resilience characteristics. Theseare properties that are particularly desirable in a number ofthermoplastic fields, including the field of golf ball manufacturing.

When utilized in the construction of the inner layer of a multi-layeredgolf ball, it has been found that the acrylic acid based high acidionomers extend the range of hardness beyond that previously obtainablewhile maintaining the beneficial properties (i.e. durability, click,feel, etc.) of the softer low acid ionomer covered balls, such as ballsproduced utilizing the low acid ionomers disclosed in U.S. Pat. Nos.4,884,814 and 4,911,451. By using these high acid ionomer resins,harder, stiffer inner cover layers having higher C.O.R.s, and thuslonger distance, can be obtained.

More preferably, it has been found that when two or more of theabove-indicated high acid ionomers, particularly blends of sodium andzinc high acid ionomers, are processed to produce the covers ofmulti-layered golf balls, (for example, the inner cover layer or layersherein) the resulting golf balls will travel further than previouslyknown multi-layered golf balls produced with low acid ionomer resincovers due to the balls' enhanced coefficient of restitution values.

Alternatively, if the inner cover layer comprises a low acid, the lowacid ionomers which may be suitable for use in formulating the innerlayer compositions of the subject invention are ionic copolymers whichare the metal, (sodium, zinc, magnesium, etc.), salts of the reactionproduct of an olefin having from about 2 to 8 carbon atoms and anunsaturated monocarboxylic acid having from about 3 to 8 carbon atoms.Preferably, the ionomeric resins are copolymers of ethylene and eitheracrylic or methacrylic acid. In some circumstances, an additionalcomonomer such as an acrylate ester (for example, iso- orn-butylacrylate, etc.) can also be included to produce a softerterpolymer. The carboxylic acid groups of the copolymer are partiallyneutralized (for example, approximately 10 to 100%, preferably 30 to70%) by the metal ions. Each of the low acid ionomer resins which may beincluded in the inner layer cover compositions of the invention contains16% by weight or less of a carboxylic acid.

The inner layer compositions include the low acid ionomers such as thosedeveloped and sold by E.I. DuPont de Nemours & Company under thetrademark Surlyn® and by Exxon Corporation under the trademarks Escor®or Iotek®, or blends thereof.

The low acid ionomer resins available from Exxon under the designationEscor® and/or Iotek®, are somewhat similar to the low acid ionomericresins available under the Surlyn® trademark. However, since theEscor®/Iotek® ionomeric resins are sodium or zinc salts ofpoly(ethylene-acrylic acid) and the Surlyn® resins are zinc, sodium,magnesium, etc. salts of poly(ethylene-methacrylic acid), distinctdifferences in properties exist.

When utilized in the construction of the inner layer of a multi-layeredgolf ball, it has been found that the low acid ionomer blends extend therange of compression and spin rates beyond that previously obtainable.More preferably, it has been found that when two or more low acidionomers, particularly blends of sodium and zinc ionomers, are processedto produce the covers of multi-layered golf balls, (for example, theinner cover layer herein) the resulting golf balls will travel furtherand at an enhanced spin rate than previously known multi-layered golfballs. Such an improvement is particularly noticeable in enlarged oroversized golf balls.

In one embodiment of the inner cover layer, a blend of high and low acidionomer resins is used. These can be the ionomer resins described above,combined in a weight ratio which preferably is within the range of 10 to90 to 90 to 10 high and low acid ionomer resins.

Another embodiment of the inner cover layer is primarily or fullynon-ionomeric thermoplastic material. Suitable non-ionomeric materialsinclude metallocene catalyzed polyolefins or polyamides,polyamide/ionomer blends, polyphenylene ether/ionomer blends, etc.,which have a Shore D hardness of at least 60 (or at least about 80 ShoreC) and a flex modulus of greater than about 15,000, more preferablyabout 30,000 psi, or other hardness and flex modulus values which arecomparable to the properties of the ionomers described above. Othersuitable materials include but are not limited to thermoplastic orthermosetting polyurethanes, thermoplastic block polyesters, forexample, a polyester elastomer such as that marketed by DuPont under thetrademark Hytrel®, or thermoplastic block polyamides, for example, apolyether amide such as that marketed by Elf Atochem S.A. under thetrademark Pebax®, a blend of two or more non-ionomeric thermoplasticelastomers, or a blend of one or more ionomers and one or morenon-ionomeric thermoplastic elastomers. These materials can be blendedwith the ionomers described above in order to reduce cost relative tothe use of higher quantities of ionomer.

A golf ball inner cover layer according to the present invention formedfrom a polyurethane material typically contains from about 0 to about 60weight percent of filler material, more preferably from about 1 to about30 weight percent, and most preferably from about 1 to about 20 weightpercent.

Outer Cover Layer

While the core with the hard inner cover layer formed thereon providesthe multi-layer golf ball with power and distance, the outer cover layer16 is preferably comparatively softer than the inner cover layer. Thesoftness provides for the feel and playability characteristics typicallyassociated with balata or balata-blend balls. The outer cover layer orply is comprised of a relatively soft, low modulus (about 1,000 psi toabout 30,000 psi, preferably about 5,000 psi to about 20,000)polyurethane, polyurea or polyurethane/polyurea, or a blend of two ormore polyurethanes, or a blend of one or more ionomers or one or morenon-ionomeric thermoplastic materials with a polyurethane, preferably athermoplastic polyurethane. The outer layer is 0.005 to about 0.150inches in thickness, preferably 0.010 to 0.075 inches in thickness, moredesirably 0.015 to 0.050 inches in thickness, but thick enough toachieve desired playability characteristics while minimizing expense.Thickness is defined as the average thickness of the non-dimpled areasof the outer cover layer. The outer cover layer 16 has a Shore Dhardness of less than 60 (or less than about 90 Shore C), and morepreferably 55 or less (or about 85 to 88 Shore C or less). If the outerlayer is too thin, it is very difficult to accurately measure the ShoreD, and sometimes the Shore C, of the outer layer as the layer maypuncture. Additionally, if the inner layer and/or core is harder thanthe outer layer, this will sometimes influence the reading. If the ShoreC or Shore D is measured on a plaque of material, different values mayresult.

The outer cover layer of the invention is formed over a core to resultin a golf ball having a coefficient of restitution of at least 0.770,more preferably at least 0.780, and most preferably at least 0.790. Thecoefficient of restitution of the ball will depend upon the propertiesof both the core and the cover. The PGA compression of the golf ball is100 or less, and preferably is 90 or less.

In a preferred embodiment, the outer cover layer comprises apolyurethane, a polyurea or a blend of polyurethanes/polyureas.Polyurethanes/polyureas are polymers that are used to form a broad rangeof products. They are generally formed by mixing two primary ingredientsduring processing. For the most commonly used polyurethanes, the twoprimary ingredients are a polyisocyanate (for example, diphenylmethanediisocyanate monomer (“MDI”) and toluene diisocyanate (“TDI”) and theirderivatives) and a polyol (for example, a polyester polyol or apolyether polyol). Various chain extenders, known in the art, are alsocommonly used.

A wide range of combinations of polyisocyanates and polyols, as well asother ingredients, are available. Furthermore, the end-use properties ofpolyurethanes can be controlled by the type of polyurethane utilized,such as whether the material is thermoset (cross-linked molecularstructure) or thermoplastic (linear molecular structure).

Cross-linking occurs between the isocyanate groups (—NCO) and thepolyol's hydroxyl end-groups (—OH), and/or with already formed urethanegroups. Additionally, the end-use characteristics of polyurethanes canalso be controlled by different types of reactive chemicals andprocessing parameters. For example, catalysts are utilized to controlpolymerization rates. Depending upon the processing method, reactionrates can be very quick (as in the case for some reaction injectionmolding systems (“RIM”) or may be on the order of several hours orlonger (as in several coating systems). Consequently, a great variety ofpolyurethanes are suitable for different end-uses.

Polyurethanes are typically classified as thermosetting orthermoplastic. A polyurethane becomes irreversibly “set” when apolyurethane prepolymer is cross-linked with a polyfunctional curingagent, such as a polyamine or a polyol. The prepolymer typically is madefrom polyether or polyester. Diisocyanate polyethers are typicallypreferred because of their hydrolytic properties.

The physical properties of thermoset polyurethanes are controlledsubstantially by the degree of cross-linking. Tightly cross-linkedpolyurethanes are fairly rigid and strong. A lower amount ofcross-linking results in materials that are flexible and resilient.Thermoplastic polyurethanes have some cross-linking, but primarily byphysical means. The cross-link bonds can be reversibly broken byincreasing temperature, as occurs during molding or extrusion. In thisregard, thermoplastic polyurethanes can be injection molded, andextruded as sheet and blow film. They can be used up to about 350° F. to450° F. and are available in a wide range of hardnesses.

Polyurethane materials suitable for the present invention are formed bythe reaction of a polyisocyanate, a polyol, and optionally one or morechain extenders. The polyol component includes any suitable polyether-or polyester-polyol. Additionally, in an alternative embodiment, thepolyol component is polybutadiene diol. The chain extenders include, butare not limited, to diols, triols and amine extenders. Any suitablepolyisocyanate may be used to form a polyurethane according to thepresent invention. The polyisocyanate is preferably selected from thegroup of diisocyanates including, but not limited, to4,4′-diphenylmethane diisocyanate (“MDI”); 2,4-toluene diisocyanate(“TDI”); m-xylylene diisocyanate (“XDI”); methylene bis-(4-cyclohexylisocyanate) (“HMDI”); hexamethylene diisocyanate (“HDI”);naphthalene-1,5,-diisocyanate (“NDI”); 3,3′-dimethyl-4,4′-biphenyldiisocyanate (“TODI”); 1,4-diisocyanate benzene (“PPDI”);phenylene-1,4-diisocyanate; and 2,2,4- or 2,4,4-trimethyl hexamethylenediisocyanate (“TMDI”).

Other less preferred diisocyanates include, but are not limited to,isophorone diisocyanate (“IPDI”); 1,4-cyclohexyl diisocyanate (“CHDI”);diphenylether-4,4′-diisocyanate; p,p′-diphenyl diisocyanate; lysinediisocyanate (“LDI”); 1,3-bis(isocyanato methyl)cyclohexane; andpolymethylene polyphenyl isocyanate (“PMDI”).

One polyurethane component that can be used in the present inventionincorporates TMXDI (“META”) aliphatic isocyanate (Cytec Industries, WestPaterson, N.J.). Polyurethanes based on meta-tetramethylxylylenediisocyanate (TMXDI) can provide improved gloss retention UV lightstability, thermal stability, and hydrolytic stability. Additionally,TMXDI (“META”) aliphatic isocyanate has demonstrated favorabletoxicological properties. Furthermore, because it has a low viscosity,it is usable with a wider range of diols (to polyurethane) and diamines(to polyureas). If TMXDI is used, it typically, but not necessarily, isadded as a direct replacement for some or all of the other aliphaticisocyanates in accordance with the suggestions of the supplier. Becauseof slow reactivity of TMXDI, it may be useful or necessary to usecatalysts to have practical demolding times. Hardness, tensile strengthand elongation can be adjusted by adding further materials in accordancewith the supplier's instructions.

The polyurethane, polyurea or polyurethane/polyurea which is selectedfor use as a golf ball cover preferably has a Shore D hardness of fromabout 10 to about 60, more preferably from about 25 to about 60, andmost preferably from about 30 to about 55 for a soft cover layer. Thepolyurethane, polyurea or polyurethane/polyurea which is to be used fora cover layer preferably has a flex modulus from about 1 to about 310Kpsi, more preferably from about 5 to about 100 Kpsi, and mostpreferably from about 5 to about 20 Kpsi for a soft cover layer and 30to 70 Kpsi for a hard cover layer. Accordingly, covers comprising thesematerials exhibit similar properties. The polyurethane preferably hasgood light fastness.

Non-limiting examples of a polyurethane, polyurea orpolyurethane/polyurea suitable for use in the outer cover layer includea thermoplastic polyester polyurethane such as Bayer Corporation'sTexin® polyester polyurethane (such as Texin® DP7-1097, Texin® 285 andTexin® 245 grades). Optionally, the thermoplastic polyurethane materialmay also be blended with a soft ionomer or other ionomeric andnon-ionomeric polymeric fillers or additive materials. For example,polyamides blend well with soft ionomer.

According to Bayer Corporation, Texin® DP7-1097 has the followingproperties:

TABLE 1 Properties of Texin ® DP7-1097 Tensile Strength (ASTM D412) 6000lb/in² @50% (ASTM D412) 875 lb/in² @200% (ASTM D412) 950 lb/in² @300%(ASTM D412) 2200 lb/in² Ultimate Elongation (ASTM D412) 450% FlexuralModulus (ASTM D790) 158° F. (70° C.) 3841 lb/in² 73° F. (23° C.) 6500lb/in² −22° F. (−30° C.) 57400 lb/in² Hardness (Shore A/Shore D) 90/40Bayshore Resilience (ASTM D2632)  35% Solubility in Water Insoluble TearStrength, Die “C” (ASTM D624) 600 lbf/in Specific Gravity (ASTM D792)1.20 Vicat Softening Temp. (ASTM D1525) 216° F. Melt Index 7-14 g/10 minat 200° C. and 8.7 kg, L/D = 4 (Method 1103-A)

According to Bayer Corporation, Texin® 245 has the following properties:

TABLE 2 Properties of Texin ® 245 Melt Flow 20-40 (230° C., 1.2 kg load)Hardness 40-50D Tensile Strength 4000 psi Minimum 100% Modulus 1090-1400psi

The melt indexes of the base thermoplastic polyurethanes received fromBayer Corporation are then increased to the following specifications:

TPU Melt Index (“MI”) Specifications

A. DP7-1097

-   As received from Bayer Corporation: 7-14, measured at 200 C, 8.7 kg.    load-   “Refined” or extruded specification: 30-50, measured at 200 C, 8.7    kg. load-   % flow increase: 114%-614%    B. Texin 245-   As received from Bayer Corporation: 20-40, measured at 230 C, 1.2    kg. load-   “Refined” specification: 30-50, measured at 210 C, 8.7 kg. load-   % flow increase: Approximately 100%

General TPU Extrusion Conditions

-   -   dry material below 0.03% moisture    -   single screw extruder, with a single stage screw having an L/D        of at least 24:1 and a compression ratio of 3:1    -   processing temps.        -   hopper: 180-220 F        -   rear: 360-390 F        -   middle: 360-400 F        -   front: 360-410 F        -   adapter: 365-410 F        -   die: 370-415 F        -   melt: 385-465 F    -   cushion—0.125″ max.    -   back pressure—200 psi. max.    -   screw speed—40-80 rpm    -   screen packs—optional

Procedure for Raising Melt Index (“M.I.”) to Desired RefinedSpecification of 30-50

-   1. Measure M.I. of dried material as received from Bayer    Corporation;-   2. Adjust extruder machine settings to achieve a nominal M.I. 40,    measured at the appropriate test conditions for either DP7-1097 or    Texin 245; and-   3. Periodically check the M.I. throughout the extrusion run to    ensure a target M.I. value of 40.

When used for golf ball cover compositions, the referenced thermoplasticpolyurethane material is blended with masterbatch (“MB”), the blendincludes the refined thermoplastic polyurethane material (81% of thefinal blend) plus a white masterbatch (19% of the final blend) is asfollows:Refined DP7-1097(81%)+MB(19%)=35-85 at 200 C, 8.7 kg. (w/o MB, therefined material M.I. is 30-50).Refined Texin 245(81%)+MB(19%)=35-85 at 210 C, 8.7 kg. (w/o MB, therefined material M.I. is 30-50)

As noted, the melt index of the final blends containing MB increase, duein part to the package additives. These additives tend to act likeplasticizers, causing an increase in the melt index. The masterbatch(MB) formulas are as follows:

TPU White Masterbatch Formulation (Texin DP7-1097)

DESCRIPTION GRAMS UV PACKAGE 4.038 AO PACKAGE 399.32 TRONOX 110/KEMIRA110 11.923 ULTRA BLUE PIGMENT 200.52 TEXIN DP7-1097 83.376

TPU White Masterbatch Formulation (Texin 245)

DESCRIPTION GRAMS UV PACKAGE 4.038 AO PACKAGE 399.32 TRONOX 110/KEMIRA110 11.923 ULTRA BLUE PIGMENT 401.02 TEXIN 245 83.159

Other soft, relatively low modulus non-ionomeric thermoplasticpolyurethanes may also be utilized to produce the outer cover layers aslong as the non-ionomeric materials exhibit the desired high or enhancedmelt indexes and produce the playability and durability characteristicsdesired. These include, but are not limited to thermoplasticpolyurethanes such as the Pellethane® thermoplastic polyurethanes fromDow Chemical Co.

Typically, there are two classes of thermoplastic polyurethanematerials: aliphatic polyurethanes and aromatic polyurethanes. Thealiphatic materials are produced from a polyol or polyols and aliphaticisocyanates, such as H₁₂MDI or HDI, and the aromatic materials areproduced from a polyol or polyols and aromatic isocyanates, such as MDIor TDI. The thermoplastic polyurethanes may also be produced from ablend of both aliphatic and aromatic materials, such as a blend of HDIand TDI with a polyol or polyols.

Generally, the aliphatic thermoplastic polyurethanes are lightfast,meaning that they do not yellow appreciably upon exposure to ultravioletlight. Conversely, aromatic thermoplastic polyurethanes tend to yellowupon exposure to ultraviolet light. One method of stopping the yellowingof the aromatic materials is to paint the outer surface of the finishedball with a coating containing a pigment, such as titanium dioxide, sothat the ultraviolet light is prevented from reaching the surface of theball. Another method is to add UV absorbers and stabilizers to the clearcoating(s) on the outer cover, as well as to the thermoplasticpolyurethane material itself. By adding UV absorbers and stabilizers tothe thermoplastic polyurethane and the coating(s), aromaticpolyurethanes can be effectively used in the outer cover layer of golfballs. This is advantageous because aromatic polyurethanes typicallyhave better scuff resistance characteristics than aliphaticpolyurethanes, and the aromatic polyurethanes are typically lower costthan aliphatic polyurethanes.

Other suitable polyurethane materials for use in the present inventiongolf balls include reaction injection molded (“RIM”) polyurethanes. RIMis a process by which highly reactive liquids are injected into a closedmold, mixed usually by impingement and/or mechanical mixing in anin-line device such as a “peanut mixer,” where they polymerize primarilyin the mold to form a coherent, one-piece molded article. The RIMprocess usually involves a rapid reaction between one or more reactivecomponents such as polyether- or polyester-polyol, polyamine, or othermaterial with an active hydrogen, and one or more isocyanate-containingconstituents, often in the presence of a catalyst. The constituents arestored in separate tanks prior to molding and may be first mixed in amix head upstream of a mold and then injected into the mold. The liquidstreams are metered in the desired weight to weight ratio and fed intoan impingement mix head, with mixing occurring under high pressure, forexample, 1,500 to 3,000 psi. The liquid streams impinge upon each otherin the mixing chamber of the mix head and the mixture is injected intothe mold. One of the liquid streams typically contains a catalyst forthe reaction. The constituents react rapidly after mixing to gel andform polyurethane polymers. Polyureas, epoxies, and various unsaturatedpolyesters also can be molded by RIM.

Non-limiting examples of suitable RIM systems for use in the presentinvention are Bayflex® elastomeric polyurethane RIM systems, Baydur® GSsolid polyurethane RIM systems, Prism® solid polyurethane RIM systems,all from Bayer Corp. (Pittsburgh, Pa.), Spectrim® reaction moldablepolyurethane and polyurea systems from Dow Chemical USA (Midland,Mich.), including Spectrim® MM 373-A (isocyanate) and 373-B (polyol),and Elastolit® SR systems from BASF (Parsippany, N.J.). Preferred RIMsystems include Bayflex® MP-5000 and Bayflex® 110-50, filled andunfilled. Further preferred examples are polyols, polyamines andisocyanates formed by processes for recycling polyurethanes andpolyureas. Additionally, these various systems may be modified byincorporating a butadiene component in the diol agent.

Another embodiment is a golf ball in which at least one of the innercover layer and/or the outer cover layer comprises afast-chemical-reaction-produced component. This component comprises atleast one material selected from the group consisting of polyurethane,polyurea, polyurethane ionomer, epoxy, and unsaturated polyesters, andpreferably comprises polyurethane. A particularly preferred form of theinvention is a golf ball with a cover comprising polyurethane.

The polyol component typically contains additives, such as stabilizers,flow modifiers, catalysts, combustion modifiers, blowing agents,fillers, pigments, optical brighteners, and release agents to modifyphysical characteristics of the cover. Polyurethane/polyurea constituentmolecules that were derived from recycled polyurethane can be added inthe polyol component.

A golf ball outer cover layer according to the present invention formedfrom a polyurethane material typically contains from about 0 to about 20weight percent of filler material, more preferably from about 1 to about10 weight percent, and most preferably from about 1 to about 5 weightpercent.

Moreover, in alternative embodiments, either the inner and/or the outercover layer may also additionally comprise up to 100 wt % of a soft, lowmodulus, non-ionomeric thermoplastic or thermoset material.Non-ionomeric materials are suitable so long as they produce theplayability and durability characteristics desired without adverselyaffecting the enhanced travel distance characteristic produced by thehigh acid ionomer resin composition. These include but are not limitedto styrene-butadiene-styrene block copolymers, including functionalizedstyrene-butadiene-styrene block copolymers,styrene-ethylene-butadiene-styrene (SEBS) block copolymers such asKraton® materials from Shell Chem. Co., and functionalized SEBS blockcopolymers; metallocene catalyzed polyolefins; ionomer/rubber blendssuch as those in Spalding U.S. Pat. Nos. 4,986,545; 5,098,105 and5,187,013; silicones; and Hytrel® polyester elastomers from DuPont andPebax® polyetheramides from Elf Atochem S.A. A preferred non-ionomericmaterial suitable for the inner and/or outer cover layer includespolyurethane.

Additional materials may also be added to the inner and outer coverlayer of the present invention as long as they do not substantiallyreduce the playability properties of the ball. Such materials includedyes (for example, Ultramarine Blue™ sold by Whittaker, Clark, andDaniels of South Plainsfield, N.J.) (see U.S. Pat. No. 4,679,795);pigments such as titanium dioxide, zinc oxide, barium sulfate and zincsulfate; UV absorbers; antioxidants; antistatic agents; and stabilizers.Moreover, the cover compositions of the present invention may alsocontain softening agents such as those disclosed in U.S. Pat. Nos.5,312,857 and 5,306,760, including plasticizers, metal stearates,processing acids, etc., and reinforcing materials such as glass fibersand inorganic fillers, as long as the desired properties produced by thegolf ball covers of the invention are not impaired.

In a preferred embodiment, the outer cover layer additionally comprisesone or more isocyanates to improve the scuff resistance of the outercover layer. The isocyanate further cross-links the cover material toprovide additional scuff resistance while maintaining the otherdesirable features of the cover, such as softness and feel. Theisocyanate is added to the outer cover layer by any suitable methodknown in the art, although dipping, wiping, soaking, brushing orspraying the golf ball in or with the isocyanate is preferred. Themethod of adding the isocyanate, or mixtures thereof, to the cover layeris discussed in more detail below.

The isocyanate that is added to the cover layer to improve scuffresistance can be any aliphatic or aromatic isocyanate or diisocyanateor blends thereof known in the art. Examples of suitable isocyanatesinclude, but are not limited to, 4,4′-diphenylmethane diisocyanate(“MDI”); 2,4-toluene diisocyanate (“TDI”); m-xylylene diisocyanate(“XDI”); methylene bis-(4-cyclohexyl isocyanate) (“HMDI”); hexamethylenediisocyanate (“HDI”); naphthalene-1,5,-diisocyanate (“NDI”);3,3′-dimethyl-4,4′-biphenyl diisocyanate (“TODI”); 1,4-diisocyanatebenzene (“PPDI”); phenylene-1,4-diisocyanate; and 2,2,4- or2,4,4-trimethyl hexamethylene diisocyanate (“TMDI”). Other lesspreferred diisocyanates include, but are not limited to, isophoronediisocyanate (“IPDI”); 1,4-cyclohexyl diisocyanate (“CHDI”);diphenylether-4,4′-diisocyanate; p,p′-diphenyl diisocyanate; lysinediisocyanate (“LDI”); 1,3-bis (isocyanato methyl) cyclohexane;polymethylene polyphenyl isocyanate (“PMDI”); andmeta-tetramethylxylylene diisocyanate (“TMXDI”). Preferably, thediisocyanate is MDI. The term “isocyanate” as used herein includes allof these compounds and other isocyanates.

As mentioned generally above, the isocyanate or diisocyanate used mayhave a solids content in the range of about 1 to about 100 weight %,preferably about 5 to about 50 weight %, most preferably about 10 toabout 30 weight %. If it is necessary to adjust the solids content, anysuitable solvent (such as ketone and acetate) that will allowpenetration of the isocyanate into the polyurethane cover materialwithout causing distortion may be used.

More preferably, the isocyanate utilized is Mondur ML™, an aromaticdiisocyanate manufactured by the Bayer Corporation. According to Bayer,Mondur ML™ is an isomer mixture of diphenyl methane diisocyanate (MDI)containing a high percentage of 2,4 isomer. More particularly, MondurML™ reportedly has the following specifications and proportions:

A. PRODUCT SPECIFICATIONS Assay, wt. % 99.5 minimum 2′,4′ isomercontent, % 50-60 Acidity as HCI, ppm 30 maximum Dimer, wt. % 0.3 maximumB. TYPICAL PROPERTIES* Appearance Clear to light yellow Specific Gravity@ 25° C. 1.19 liquid Equivalent weight 125 Freezing point 59°-68° F.(15-20° C.) NCO Content, % 33.4-33.6 Flash point (Setaflash) 388° F.(198° C.) Viscosity @25° C. 10 Equivalent wt., avg. (as supplied) 125mPa*s Weight per gallon, lb. 9.9 @25° C. *These items are provided asgeneral information only. They are approximate values and are notconsidered part of the product specification.Core

The cores of the inventive golf balls typically have a coefficient ofrestitution of about 0.750 or more, more preferably 0.770 or more and aPGA compression of about 90 or less, and more preferably 70 or less.Furthermore, in some applications it may be desirable to provide a corewith a coefficient of restitution of about 0.780 to 0.790 or more. Thecore used in the golf ball of the invention preferably is a solid. Theterm “solid cores” as used herein refers not only to one piece cores butalso to those cores having a separate solid layer beneath the covers andover the central core. The cores have a weight of 25-40 grams andpreferably 30-40 grams. When the golf ball of the invention has a solidcore, this core can be compression molded from a slug of uncured orlightly cured elastomer composition comprising a high cis contentpolybutadiene and a metal salt of an α, β, ethylenically unsaturatedcarboxylic acid such as zinc mono- or diacrylate or methacrylate. Toachieve higher coefficients of restitution and/or to increase hardnessin the core, the manufacturer may include a small amount of a metaloxide such as zinc oxide. In addition, larger amounts of metal oxidethan are needed to achieve the desired coefficient may be included inorder to increase the core weight so that the finished ball more closelyapproaches the U.S.G.A. upper weight limit of 1.620 ounces. Non-limitingexamples of other materials which may be used in the core compositionincluding compatible rubbers or ionomers, and low molecular weight fattyacids such as stearic acid. Free radical initiator catalysts such asperoxides are admixed with the core composition so that on theapplication of heat and pressure, a curing or cross-linking reactiontakes place.

A thread wound core may comprise a liquid, solid, gel or multi-piececenter. The thread wound core is typically obtained by winding a threadof natural or synthetic rubber, or thermoplastic or thermosettingelastomer such as polyurethane, polyester, polyamide, etc. on a solid,liquid, gel or gas filled center to form a thread rubber layer that isthen covered with one or more mantle or cover layers. Additionally,prior to applying the cover layers, the thread wound core may be furthertreated or coated with an adhesive layer, protective layer, or anysubstance that may improve the integrity of the wound core duringapplication of the cover layers and ultimately in usage as a golf ball.

Method of Making Golf Ball

In preparing golf balls in accordance with the present invention, aninner cover layer, preferably a hard inner cover layer, is molded (forexample, by injection molding or by compression molding) about a core(preferably a solid core). A comparatively softer outer layer is molded(for example, by injection molding or by reaction injection molding)over the inner layer.

The solid core for the multi-layer ball is about 1.2 to 1.6 inches indiameter, although it may be possible to use cores in the range of about1.0 to 2.0 inches. Conventional solid cores are typically compression orinjection molded from a slug or ribbon of uncured or lightly curedelastomer composition comprising a high cis content polybutadiene and ametal salt of an α, β, ethylenically unsaturated carboxylic acid such aszinc mono or diacrylate or methacrylate. To achieve higher coefficientsof restitution in the core, the manufacturer may include fillers such assmall amounts of a metal oxide such as zinc oxide. In addition, largeramounts of metal oxide than those that are needed to achieve the desiredcoefficient are often included in conventional cores in order toincrease the core weight so that the finished ball more closelyapproaches the U.S.G.A. upper weight limit of 1.620 ounces. Othermaterials may be used in the core composition including compatiblerubbers or ionomers, and low molecular weight fatty acids such asstearic acid. Free radical initiators such as peroxides are admixed withthe core composition so that on the application of heat and pressure, acomplex curing cross-linking reaction takes place.

In some embodiments, the inner cover layer(s) that is molded over thecore is about 0.010 inches to about 0.150 inches in thickness, morepreferably about 0.020 to about 0.10 inches thick. The inner ball thatincludes the core and inner cover layer(s) preferably has a diameter inthe range of 1.25 to 1.64 inches. The outer cover layer is 0.005 inchesto 0.075 inches in thickness, preferably 0.010 to 0.050 inches thick,more preferably 0.010 to 0.040 inches thick, and most preferably 0.010to 0.030 inches thick. Together, the core, the inner cover layer(s) andthe outer cover layer combine to form a ball having a diameter of 1.680inches or more, the minimum diameter permitted by the rules of theUnited States Golf Association and weighing no more than 1.62 ounces.

In a particularly preferred embodiment of the invention, the golf ballhas a dimple pattern that provides dimple coverage of 65% or more,preferably 75% or more, and more preferably 85% or more. In a preferredembodiment of the invention, there are greater than 300 dimples,preferably from about 300 to about 500 dimples.

After the outer cover layer, formed from a polyurethane/polyureamaterial, is molded on the golf ball, the isocyanate is added to thecover. The isocyanate is preferably added by dipping, soaking orspraying the golf ball in or with the isocyanate solution for about 1 to10 minutes, more preferably about 1 to 5 minutes. If the golf ball istreated too long, the cover could swell and possibly delaminate. Theisocyanate solution may be any desired isocyanate or diisocyanatesolution, and the solids content is preferably 1 to 100 weight percent,preferably 5 to 50 weight percent, more preferably 15 to 30 weightpercent, and most preferably 16 to 24 weight percent. The golf balls arepreferably heated to a temperature such as 110° F. to 120° F. beforeadding the isocyanate to facilitate the penetration of the isocyanateinto the cover, although heating is not required. After the golf ballsof the invention are dipped in the isocyanate solution for theappropriate amount of time, the balls are air dried for approximately 30minutes to 24 hours, more preferably 1 to 2 hours, and most preferablyat least about 1 hour. The golf balls are then post-cured to promotecross-linking of the cover material, preferably at a temperature ofabout 150° F. to 250° F., more preferably about 175° F. for about 2 to24 hours, more preferably about 4 hours. After post-curing, the golfballs may be cleaned using a suitable cleaner, such as an alcohol, ifneeded. An example of a suitable alcohol is isopropanol, although anysuitable alcohol that does not damage or react with the cover materialmay be used. After addition of the isocyanate to the cover, the ballsare finished as desired.

In a preferred embodiment, the golf ball typically is coated with adurable, abrasion-resistant, relatively non-yellowing finish coat orcoats if necessary. The finish coat or coats may have some opticalbrightener added to improve the brightness of the finished golf ball. Ina preferred embodiment, from 0.001 to about 10% optical brightener maybe added to one or more of the finish coatings. Preferred finishcoatings are solvent based urethane coatings known in the art.

The golf balls of the present invention can be produced by moldingprocesses, which include but are not limited to those that are currentlywell known in the golf ball art. For example, the golf balls can beproduced by injection molding or compression molding the novel covercompositions around a wound or solid molded core to produce an innerball, which typically has a diameter of about 1.50 to 1.67 inches. Theouter layer is subsequently molded over the inner layer to produce agolf ball having a diameter of about 1.680 inches or more. Althougheither solid cores or wound cores can be used in the present invention,as a result of their lower cost and superior performance, solid moldedcores are preferred over wound cores. The standards for both the minimumdiameter and maximum weight of the balls are established by the UnitedStates Golf Association (U.S.G.A.).

In compression molding, the inner cover composition is formed viainjection molding at about 380° F. to about 450° F. into smooth surfacedhemispherical shells which are then positioned around the core in a moldhaving the desired inner cover thickness and subjected to compressionmolding at 200° F. to 300° F. for about 2 to 10 minutes, followed bycooling at 50° F. to 70° F. for about 2 to 7 minutes to fuse the shellstogether to form a unitary intermediate ball. In addition, theintermediate balls may be produced by injection molding wherein theinner cover layer is injected directly around the core placed at thecenter of an intermediate ball mold for a period of time in a moldtemperature of from 50° F. to about 100° F. Subsequently, the outercover layer is molded about the core and the inner layer by similarmolding techniques to form a dimpled golf ball of a diameter of 1.680inches or more. To improve the adhesion between the inner cover layerand the outer cover layer, an adhesion promoter may be used. Someadhesion promoters, such as abrasion of the surface, corona treatment,and the like, are known in the art. A preferred adhesion promoter is achemical adhesion promoter, such as a silane or other silicon compound,preferably N-(2-aminoethyl)3-aminopropyltrimethoxysilane. Theintermediate golf ball (core and inner cover layer) may be dipped orsprayed with the chemical, and then the outer cover layer is formed overthe treated inner cover layer.

After molding, the golf balls produced may undergo various furtherprocessing steps such as buffing, painting and marking as disclosed inU.S. Pat. No. 4,911,451.

The resulting golf ball produced from the hard inner layer and therelatively softer, low flexural modulus outer layer which additionallycomprises an isocyanate provide for an improved multi-layer golf ballwhich provides for desirable coefficient of restitution and durabilityproperties while at the same time offering the feel and spincharacteristics associated with soft balata and balata-like covers ofthe prior art.

Additionally, golf balls of the present invention that comprisepolyurethane in any of the inner and outer cover layers may be producedby a reaction injection molding process (RIM) as previously described.

Golf balls and, more specifically, cover layers formed by RIM arepreferably formed by the process described in application Ser. No.09/040,798, filed Mar. 18, 1998, incorporated herein by reference.

The golf balls formed according to the present invention can be coatedusing a conventional two-component spray coating or can be coated duringthe RIM process, for example, using an in-mold coating process.

The present invention includes a wide variety of strategies andtechniques for improving the scuff resistance of thermoplasticpolyurethane covers. For example, various additives could beincorporated in the cover formulation and/or utilized in apost-treatment process after formation of the ball. Such additivesinclude, but are not limited to, isocyanates, capped isocyanates,peroxides, silanes, siloxanes, unsaturated monomers and oligomers,saturated monomers and oligomers, silicones, TPU/silicone copolymers,irradiation, carboxylated monomers and oligomers or other functionalmonomers or oligomers, fillers such as reinforcing, non-reinforcing,treated or untreated, different TPU's and/or blends of TPU's with othermaterials and/or polymers (aromatic or aliphatic), and Zylon™crosslinking additives.

The present invention is further illustrated by the following examplesin which the parts of the specific ingredients are by weight. It is tobe understood that the present invention is not limited to the examples,and various changes and modifications may be made in the inventionwithout departing from the spirit and scope thereof.

EXAMPLES Example 1

Golf balls having thermoplastic polyurethane covers were made. The golfballs were made with dual cores, a high flow ionomer inner cover layer,and a thermoplastic polyurethane outer cover layer. The compositions ofthe cover layers are shown in the Tables below. The golf balls were thenheated to 110° F. to 120° F. and dipped in different solutions andconcentrations of isocyanates as shown below. The balls were dipped foreither 2 or 5 minutes. After dipping, the balls were allowed to air dryfor about one hour, and they were then placed in an oven at 180° F. forabout 16 hours. After removal from the oven, some residue was noted onsome of the balls. Three balls from each group were rinsed inisopropanol and dried with a rag. All balls were finished with aconventional clear primer and topcoat. The balls were then tested forscuff resistance. The results are shown in Table 6 below. Severalcontrol balls that were not dipped in isocyanate were also tested, andthe results are shown in Table 6 below.

The scuff resistance test was conducted in the manner described below.The balls that were tested were primed and top coated. A sharp groovedsand wedge (56 degrees loft) was mounted in a mechanical swing machine.The club swing speed used is 60 mph. After each hit, the club face isbrushed clean using a nylon bristled brush. A minimum of three samplesof each ball were tested. Each ball was hit three times at threedifferent locations so as not to overlap with other strikes. The detailsof the club face are critical, and are as follows:

Groove width—0.025 inches (cut with a mill cutter, leaving a sharp edgeto the groove; no sandblasting or post finishing should be done aftermilling);

Groove depth—0.016 inches;

Groove spacing (one groove edge to the nearest adjacent edge)—0.105inches.

For each strike, a point value should be assigned for the worst twodefects according to the following table:

Point Value Shear Defect 0 No visible defects 0.5 Lines 1 Lifts 2 BadLifts 2 Tiny (or Paint) Hairs 3 Bad Hairs 3 Shears (if land area isremoved on “hard” covers (65 Shore D+), rank as the only limit 6 (maxvalue) Bad Shears (dimples are completely removed, rank as the onlydefect)Example—a strike having a shear, tiny hairs, bad lifts and a line wouldbe ranked as a 5 (3 points for a shear and 2 points for tiny hairs)Note: The maximum value per strike is 6.After completing all strikes, determine the average point value. Thisaverage point value, or rank, can be correlated to the chart below.

Rank Average Point Value Excellent 0.0-1.0 Very Good 1.1-2.0 Good2.1-3.0 Fair 3.1-4.0 Borderline 4.1-5.0 Poor (unacceptable) 5.1-6.0

TABLE 4 Inner Cover Layer Composition Ingredient Amount (Weight %)Surlyn ® 6120 25 Surlyn ® 8140 50 Surlyn ® 9150 25

TABLE 5 Outer Cover Layer Composition Ingredient Amount (Weight %)Texin ® DP7-1097 81 Masterbatch* 19 *Masterbatch - Texin ® DP7-1097Masterbatch which consists of pigments, titanium dioxide, etc. in acarrier of the resin used in the cover layer)

TABLE 6 Scuff Test Results Name Type Sample Code % NCO % Solids Dip TimeScuff Rank Control - no dip None 0 min 5 Desmodur N-3200 Aliphatic HDI 1Orange 23.2 99.3 2 min 4 Desmodur N-3200 Aliphatic HDI 2 Orange 23.2 502 min 1.7 Desmodur N-3200 Aliphatic HDI 3 Orange 23.2 25 2 min 1.3Desmodur N-3200 Aliphatic HDI 4 Orange 23.2 10 2 min 1.8 Desmodur N-3200Aliphatic HDI 1 Orange - Rinsed 23.2 99.3 2 min 1.7 Desmodur N-3200Aliphatic HDI 2 Orange - Rinsed 23.2 50 2 min 1.8 Desmodur N-3200Aliphatic HDI 3 Orange - Rinsed 23.2 25 2 min 1.8 Desmodur N-3200Aliphatic HDI 4 Orange - Rinsed 23.2 10 2 min 1.8 Desmodur ICycloaliphatic IPDI 1 Green 37.5 99.5 2 min 5.7 Desmodur ICycloaliphatic IPDI 2 Green 37.5 50 2 min 3 Desmodur I CycloaliphaticIPDI 3 Green 37.5 25 2 min 3.3 Desmodur I Cycloaliphatic IPDI 4 Green37.5 10 2 min 4 Desmodur I Cycloaliphatic IPDI 1 Green - Rinsed 37.599.5 2 min 2.7 Desmodur I Cycloaliphatic IPDI 2 Green - Rinsed 37.5 50 2min 2 Desmodur I Cycloaliphatic IPDI 3 Green - Rinsed 37.5 25 2 min 3.2Desmodur I Cycloaliphatic IPDI 4 Green - Rinsed 37.5 10 2 min 3.7Desmodur W Hydrogenated MDI 1 Blue 31.8 99.5 2 min 4 Desmodur WHydrogenated MDI 2 Blue 31.8 50 2 min 2 Desmodur W Hydrogenated MDI 3Blue 31.8 25 2 min 2 Desmodur W Hydrogenated MDI 4 Blue 31.8 10 2 min2.3 Desmodur W Hydrogenated MDI 1 Blue - Rinsed 31.8 99.5 2 min 2Desmodur W Hydrogenated MDI 2 Blue - Rinsed 31.8 50 2 min 2.7 Desmodur WHydrogenated MDI 3 Blue - Rinsed 31.8 25 2 min 2.3 Desmodur WHydrogenated MDI 4 Blue - Rinsed 31.8 10 2 min 2.3 Isonate 125M Pure MDI1 Black 33.5 100 2 min 2.5 Isonate 125M Pure MDI 2 Black 33.5 50 2 min 2Isonate 125M Pure MDI 3 Black 33.5 25 2 min 4 Isonate 125M Pure MDI 4Black 33.5 10 2 min 4 Isonate 125M Pure MDI 1 Black - Rinsed 33.5 100 2min 1.3 Isonate 125M Pure MDI 2 Black - Rinsed 33.5 50 2 min 1.2 Isonate125M Pure MDI 3 Black - Rinsed 33.5 25 2 min 1.2 Isonate 125M Pure MDI 4Black - Rinsed 33.5 10 2 min 1.3 Isonate 125M Pure MDI 1 Black - Rinsed33.5 100 2 min 1.7 Isonate 125M Pure MDI 2 Black - Rinsed 33.5 50 2 min1.8 Isonate 125M Pure MDI 3 Black - Rinsed 33.5 25 2 min 1 Isonate 125MPure MDI 4 Black - Rinsed 33.5 10 2 min 1.2 Isonate 125M Pure MDI 1 Red33.5 25 5 min 4 Isonate 125M Pure MDI 1 Red - Rinsed 33.5 25 5 min 1.2Desmodur I Cycloaliphatic IPDI 2 Red 37.5 25 5 min 1.8 Desmodur ICycloaliphatic IPDI 2 Red - Rinsed 37.5 25 5 min 2 Desmodur N-3200Aliphatic HDI 3 Red 23.2 25 5 min 1.5 Desmodur N-3200 Aliphatic HDI 3Red - Rinsed 23.2 25 5 min 1.5 Desmodur W Hydrogenated MDI 4 Red 31.8 255 min 2.7 Desmodur W Hydrogenated MDI 4 Red - Rinsed 31.8 25 5 min 2.3

As indicated in the results, the golf balls that were dipped in the MDIsolution and rinsed in isopropanol (Black, Rinsed) had the best overallscuff ranking. Within the groups, the golf balls dipped in the 25%solids MDI that were the best. All of the groups of golf balls hadbetter scuff results than the control balls, which were not dipped.

The procedure for dipping was further refined for production to improveefficiency and reduce the processing time. The inventors found that theballs could be oven dried for only 4 hours at 175° F. instead of 16hours at 180° F., and the isopropanol rinse could be eliminated withoutadversely affecting the final scuff results.

Example 2 Unrefined or Processed Material with No Post-Treatment(Isocyanate Dip)

A series of golf balls were manufactured using base, or unrefined (orprocessed) materials. The nature of the balls' construction and theproperties produced thereby are set forth below.

Cover Type, Shore D, Core Type, Size, Riehle Mantle Type, ThicknessThickness Letter Code STP90, 1.470″, 136 STP90, .050″ STP90, 47D, .055″A STP90, 1.470″, 136 STP90, .050″ STP90, 47D, .055″ B STP, 1.510″,120-122 STP, .0425″ STP, 50D, .0425″ C STP, 1.510″, 120-122 STP, .0425″STP, 50D, .0425″ D STP*, 1.540″, 94 STP, .035″ Experimental Ionomerblend E 1, 50D, .035″ STP*, 1.540″, 94 STP, .035″ Experimental Ionomerblend F 1, 50D, .035″ STP**, 1.540″, 94 STP, .035″ DP7-1097, 50D, .035″G STP**, 1.540″, 94 STP, .035″ DP7-1097, 50D, .035″ H STU*, 1.540″, 94STU, .035″ Experimental Ionomer blend I 2, 47D, .035″ STU*, 1.540″, 94STU, .035″ Experimental Ionomer blend J 2, 47D, .035″ STU**, 1.540″, 94STU, .035″ Texin 285, 47D, .035″ K STU**, 1.540″, 94 STU, .035″ Texin285, 47D, .035″ L **Weight adjusted for TPU coverStatics:

Ball Size Ball Weight Ball PGA Comp COR @ 125 ft./sec. Cut Rank ScuffRank Letter Code A 1.683 45.40 74 0.7922 3 4.7 B 1.685 45.53 73 0.7916 34.7 C 1.683 45.11 79 0.8006 3 5.7 D 1.684 45.18 80 0.8010 3 5.7 E 1.68745.21 78 0.8039 3 6.0 F 1.688 45.31 79 0.8036 3 6.0 G 1.689 45.66 760.8011 2 5.0 H 1.691 45.76 76 0.8010 2 5.0 I 1.686 45.13 75 0.8027 3 5.0J 1.687 45.20 75 0.8017 3 5.0 K 1.691 45.63 73 0.8046 2 3.7 L 1.69245.73 73 0.8038 2 3.7 Controls Strata Tour Pro 90 1.682 45.66 76 0.7862NA NA Strata Tour Pro 1.684 45.12 82 0.8018 NA NA STU 1.684 45.62 820.7979 3 4.8 STU 2 1.682 45.33 86 0.8034 NA NA Titleist ProV1 1.67945.40 78 0.8037 1 3.0

Core PGA Letter Code Core Size Core Wt Comp. Core CoR A 1.468 32.34 230.7964 B 1.468 32.34 23 0.7964 C 1.508 34.17 39 0.7728 D 1.508 34.17 390.7728 E 1.541 36.16 67 0.7996 F 1.541 36.16 67 0.7996 G 1.539 35.22 660.8038 H 1.539 35.22 66 0.8038 I 1.54 36.06 64 0.7937 J 1.54 36.06 640.7937 K 1.54 35.16 61 0.7991 L 1.54 35.16 61 0.7991

Mantle PGA Letter Code Mantle Size Mantle Wt Comp Mantle CoR A 1.56838.07 52 0.7994 B 1.568 38.07 52 0.7994 C 1.593 39.28 56 0.7969 D 1.59339.28 56 0.7969 E 1.611 40.41 76 0.8105 F 1.611 40.41 76 0.8105 G 1.61239.48 73 0.8120 H 1.612 39.48 73 0.8120 I 1.611 40.28 70 0.8079 J 1.61140.28 70 0.8079 K 1.611 39.34 70 0.8131 L 1.611 39.34 70 0.8131

The results indicate that the balls of the invention (without secondaryisocyanate treatment) did have scuff and cut resistance that was similarto, if not better than, that of balls having more traditional ionomer orionomer blend covers. Furthermore, the results indicate that samples ofthe golf balls having TPU covers, G, H, K and L, alone, withoutsecondary curing, had slightly poorer scuff and cut results than thatmeasured on a commercially available ball with a cast thermosetpolyurethane cover (Titleist® ProV1). Consequently, in some instances,the addition of the secondary curing agent (such as the solution ofisocyanate) is desirable to further improve durability,

1. A golf ball comprising: a core comprising a spherical center and acore layer surrounding the spherical center, the core having a massranging from 25 grams to 40 grams; an inner cover layer disposed overthe core, the inner cover layer composed of a blend of ionomers andhaving a thickness ranging from 0.020 inch to 0.10 inch; and a coverformed over the inner cover layer, the cover composed of a thermoplasticmaterial comprising a polyurea composition having a melt index of 15g/10 min or more at a temperature of 200° C. to 210° C. and a load of8.7 kg prior to molding, the cover having a thickness of less than 0.040inch and wherein the cover is treated with a secondary curing agentcomprising an isocyanate.
 2. The golf ball of claim 1, wherein theisocyanate is MDI.
 3. A golf ball comprising: a core comprising aspherical center and a core layer surrounding the spherical center, thecore having a mass ranging from 25 grams to 40 grams; an inner coverlayer disposed over the core, the inner cover layer composed of a blendof ionomers and having a thickness ranging from 0.020 inch to 0.10 inch;and a cover formed over the inner cover layer, the cover composed of apost-molding cross-linked thermoplastic material comprising a polyesterpolyurea having a melt index of 15 g/10 min or more at a temperature of200° C. to 210° C. and a load of 8.7 kg prior to molding, the coverhaving a thickness of less than 0.040 inch and wherein the cover istreated with a secondary curing agent comprising 4,4′-diphenylmethanediisocyanate.